/*
 * Copyright (c) 2010, Michael Hengler (developer (at) hengler (dot) de),
 *                     Nikolaus Moll (developer (at) miblounge (dot) net).
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * * Neither the name of the [QTPRJ] nor the
 *   names of its contributors may be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL [QTPRJ] BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */
package joodin.impl.util;

public class StringComparator {
	private final String changed;
	private final int changeStart;
	private int changeEnd;
	
	public StringComparator(final String oldText, final String newText, final int cursorPosition)
	{
		// the string after the cursor position doesn't have any changes
		if(cursorPosition < 1){
			changeEnd = 0;
		}
		else{
			changeEnd = cursorPosition - 1;
			if(changeEnd < 0){
				changeEnd = 0;
			}
		}
		
		// compare the string from the beginning up to the char before the cursor
		// or to the end of the original string
		final int compareLength = Math.min(cursorPosition, oldText.length());

		// initialize the start 
		int start = compareLength;

		for (int i = 0; i < compareLength; i++) {
			if ((oldText.charAt(i) != newText.charAt(i))) {
				start = i;
				break;
			}
		}
//		changeStart = start;
		changeStart = 0;
		
		
		this.changed = newText.substring(changeStart, changeEnd);
	}
	
	public String getText()
	{
		return changed;
	}

	public int getChangeCount()
	{
		return changeEnd - changeStart;
	}

	public int getStart() {
		return changeStart;
	}

	public int getEnd() {
		return changeEnd;
	}
}
